The present invention relates to an epoxy resin, epoxy resin composition, cured epoxy resin and a method of manufacture thereof.
An epoxy resin composition, based on an epoxy resin containing mesogen, is characterized by excellent mechanical and thermal properties and has been studied from various aspects.
For example, the Japanese Application Patent Laid-Open Publication No. Hei 07-90052 contains the description of an epoxy resin composition whose essential components are a biphenolic epoxy resin and a polyvalent phenolic resin curing agent derived from polyvalent phenol containing two or more phenolic hydroxyl groups coupled where mutual aromatic rings are adjacent to each other.
Further, the Japanese Application-Patent Laid-Open Publication No. Hei 09-118673 and U.S. Pat. No. 5,811,504 contain a description of an epoxy resin having, in a molecule, two mesogens coupled by a folded chain.
(Problems to be Solved by the Invention)
However, since the melting point of an epoxy resin containing mesogen in a molecule is generally high, the gellation time is short for an epoxy resin composition that is mixed with an epoxy resin curing agent in a molten state, and the resultant handling difficulty has been a problem. Further, two steps are required to synthesize an epoxy resin containing, in a molecule, two mesogens coupled by a folded chain. High costs are needed in the phase of industrialization aimed at mass synthesis.
To solve these problems, it is an object of the present invention to provide an epoxy resin that contains in a molecule, two mesogens coupled by a folded chain, using a method that ensures easy synthesis of-such an epoxy resin, and to offer an epoxy resin composition based on this epoxy resin.
(Means for Solving the Problems)
The foregoing-object can be-attained by the present invention described below.
(1) An epoxy resin comprising a compound having a structure expressed by the following Chemical Formula: 
(2) A method for manufacturing an epoxy resin by reaction of (A) an epoxy resin with one mesogen contained in a molecule and (B) a compound with two elements of active hydrogen contained in a molecule, with the percentage composition of the (B) active hydrogen with respect to the (A) epoxy group being 0.25 and over, up to and including 0.7.
(3) An epoxy resin composition comprising an epoxy resin with mesogen and a curing agent for the epoxy resin characterized in that the aforementioned epoxy resin having mesogen is an epoxy resin described in the aforementioned item (1).
(4) A conductive paste comprising an epoxy resin with mesogen, a curing agent and a conducting agent characterized in that the aforementioned epoxy resin with mesogen is an epoxy resin described in the aforementioned item (1).
(5) A cured epoxy resin obtained by heating and curing an epoxy resin composition comprising an epoxy resin with mesogen and a curing agent for the epoxy resin, wherein the aforementioned epoxy resin with mesogen is an epoxy resin described in the aforementioned item (1).